Currently, Institute of Electrical and Electronics Engineers (IEEE) 802.11ah defines the wireless local area network protocol, especially for sub-1 Gigaherz (GHz) carrier frequency. Its main requirements include a longer coverage area (up to 1 kilometer (km)), a physical layer (PHY) data rate of at least 100 kilobits per second (kbps), a maximum aggregate multi-station data rate of 20 megabits per second (Mbps), use orthogonal frequency-division multiplexing (OFDM) PHY modulation, and support the number of associations beyond 2007 for outdoor applications. However, overhead is a critical issue for 802.11ah. The physical layer of 802.11ah uses a 10 times slower clock than the normal 802.11 protocol, and therefore each symbol length is 10 times longer than the normal 802.11 protocol. Efficiency of the protocol is important for 802.11ah.
An addressing method in current IEEE 802.11 protocol uses a 6 byte Media Access Control (MAC) address for both access point (AP) and station (STA). However, for each STA, practically less than 100 APs will be seen, and thus the use of a 6 Byte MAC address to indicate those APs causes too much of waste. Similarly, for each AP, practically at most several thousand STAs can be associated, and the use of a 6 byte MAC address to indicate those STAs also implicates too much of waste.
To resolve this addressing issue, the use of a partial identifier (ID) has been considered. In IEEE 802.11 TGac, instead of using a whole association ID (AID), the use of only partial information on AID, as shown in table 100 in FIG. 1, has been proposed and accepted. However, because only part of the information is used, one partial AID can indicate multiple STAs simultaneously.
An example scenario of a method 200 for sending packets with a partial ID illustrates problems with the conventional solution, as shown in FIG. 2. A STA (STA1) sends a packet with a receiver address using a partial ID. Two different receivers (STA2 and STA3) have the same partial ID that STA1 used as a receiver address, and these two STAs will respond with an acknowledgment (ACK) packet at the same time, which will result in a packet collision. As STA1 did not receive the ACK packet correctly, it will retransmit the same packet again with the same partial ID. Because the same partial ID is used, STA2 and STA3 will respond again, which will result in another packet collision. Therefore, when a collision happens due to the partial ID, it is possible that collision can happen for multiple consecutive packets or retransmissions.